A mobile device and information transmission method are provided. The information transmission method is applied to the mobile device in M2M communication and includes the steps of determining whether a base station and the mobile device support transmission of capability information of the mobile device by a General Extension Message; and determining whether the capability information of the mobile device is changed when the base station and the mobile device support transmission of the capability information by the General Extension Message, wherein when the capability information of the mobile device is changed, the changed capability information is tied up with a Registration Message and transmitted to the base station by the General Extension Message.